This invention relates to earth working machines having a support for a frame-mounted boom, and more particularly to a retainer for holding the boom support pendant pin in a fixed position.
Earth working machines such as dragline excavators generally include a boom pivotally mounted on one end of a frame that is raised to a boom operating position and mechanically held in that position by a boom support assembly.
Currently the boom support assemblies on dragline excavators utilize a gantry rising upwardly from the main frame to provide the support to the pivotally-mounted boom by means of tension members that are typically made out of wire rope, referred to herein as pendants, running from the top of the gantry out to the point of the boom. The boom point end of the pendants are attached directly to the point of the boom. The gantry end of the pendants are attached to a pendant linkage assembly having a throughbore for attachment to the top of the gantry. Typically, a dragline excavator will utilize two linkage assemblies with two pendants attached to each assembly.
At the top of the gantry there are projecting ears comprised of structural plates that have a double overlapping bore opening to receive the linkage assembly. The boom is raised until the linkage assemblies reach the top portion of the gantry structure and are adjacent to and coaxially aligned with the bores in the structural plates. A pendant pin is inserted through the bores and the linkage throughbore to hold the boom via the boom support assembly in its fixed operating position.
Referring to the prior art illustrations of FIGS. 2 and 3, a boom support assembly is generally designated by the reference numeral 20. During assembly of the boom, pendant pin 22 is inserted into bore 24, which diameter is larger than the diameter of pin 22 to ease assembly, and into the throughbore of the linkage assembly. The boom is then lowered into its operating position and the pin seats into the smaller bore 23, leaving a void 25. This pendant pin 22 must be retained in a fixed non-rotatable position to ensure that the cross-drilled lubrication hole 21 radial location is maintained away from the bending stress area of the pendant pin 22. Two retainers 26 are used to hold the pendant pin 22 in a fixed position. Retainers 26 having a plurality of bores 28 are placed against countersunk bores on the outward sides of the gantry plates 30 and against the exposed ends of the pendant pin 22. The outer diameter bores 28 align with threaded bores 32 in the gantry plates 30 and both aligned bores receive bolts 34 to hold the retainers 26 to the gantry plates 30. Inner diameter bores 27 align with threaded bores 36 in the ends of the pendant pin 22, and both aligned bores receive bolts 38 to hold the pin 22 and the retainers 26 together.
As shown in FIG. 3, retainers 26 prevent the pendant pin 22 from rotational, axial and coaxial movement, but the threaded bores 32 and the countersunk bores in gantry plates 30 produce stress concentrations in critical locations, weakening the structural gantry plates 30 themselves. Additionally, the use of boom support assembly 20 requires a great deal of machining on the retainers 26, gantry plates 30 and the pendant pin 22. This assemblage also requires additional parts (a large number of bolts) and requires time consuming assembly in the lining up of bores 28 on retainers 26 with the threaded bores 32 in the gantry plates 30, as well as bores 27 on the retainers 26 with the threaded bores 36 in the pendant pin 22.